Question: Ashley is 4 times as old as Ishaan and is also 21 years older than Ishaan. How old is Ishaan?
Explanation: We can use the given information to write down two equations that describe the ages of Ashley and Ishaan. Let Ashley's current age be $a$ and Ishaan's current age be $i$ $a = 4i$ $a = i + 21$ Now we have two independent equations, and we can solve for our two unknowns. Since we are looking for $i$ , and both of our equations have $a$ alone on one side, this is a convenient time to use elimination. Subtracting the second equation from the first equation, we get: $0 =$ $4i$ $-$ $ (i + 21)$ which combines the information about $i$ from both of our original equations. Solving for $i$ , we get: $3 i = 21$ $i = 7$.